For any task or occupation, sleep deprivation can result in the decline of alertness levels, thereby resulting in the degradation of work performance. To this end, sleeping may be considered an effective countermeasure to prevent decline in alertness levels. Two important factors related to sleeping include wake inertia and sleep inertia. Generally, wake inertia may be defined as the latency or time needed to begin sleeping while sleep inertia may refer to a post-awakening degradation of performance (i.e., “grogginess”). Furthermore, the positive effects of sleeping can depend on various factors such as the time of day, the amount of any sleep deprivation experienced, and the length of the nap. Therefore, as sleeping may provide significant improvements in alertness levels, determining the ideal sleep start time and sleep duration to afford minimum wake and sleep inertia may be important to maximizing the recovery effects of sleeping.
Furthermore, though sleep patterns may vary, it is generally accepted that individuals pass through various stages during sleep, called sleep stages. Typically, sleep may be categorized into either Rapid Eye Movement (REM) sleep or non-REM sleep. Non-REM sleep may be associated with four sleep stages, with sleep stages 1 and 2 corresponding to lighter sleep and sleep stages 3 and 4 corresponding to deeper sleep.
While a number of biological alarms that monitor sleep patterns of a user are available on the market, these alarms are primarily concerned with reducing the effects of sleep inertia associated with waking up from a night time sleep episode. Some products, for example, focus on scanning for a user's light stages of sleep (Stages 1 and 2) in the sleep cycle and waking up the user during near these moments at or near the user's scheduled wake-up time. In effect, these products attempt to reduce the sleep inertia associated with waking up from a deep stage of sleep. Notably, current products do not incorporate the influences of sleep debt and the time of day into their calculations for sleep inertia, though both factors may significantly affect sleep inertia. Furthermore, since current designs focus on night time sleep episodes, they do not take into account the wake inertia associated with day time naps where a person may have difficulty failing asleep.
Thus, a need exists for systems and methods for monitoring sleep conditions and providing optimum sleep conditions. Such systems and methods determine sleep conditions which may improve alertness such as by minimizing sleep inertia after a user awakens and minimizing wake inertia as a user prepares to fall asleep.